- Person
- Lev Landau
- Lived
- 1908–1968
- Field
- Theoretical Physics
- From
- Soviet
The story
Between 1929 and 1931 a Soviet government fellowship, supplemented by a Rockefeller Foundation grant, allowed the young Lev Landau to travel to the great centres of the new quantum physics. He worked at Niels Bohr's institute in Copenhagen on three occasions, visited Göttingen and Leipzig, worked with Paul Dirac in Cambridge and with Wolfgang Pauli in Zurich. For the rest of his life he considered himself a pupil of Bohr. During these travels he tackled a problem that classical physics could not solve: why metals are weakly repelled by magnets, a property called diamagnetism.
In 1930 he showed that, according to quantum mechanics, electrons moving in circles in a magnetic field can only have certain discrete energies. These quantised energy levels are now called Landau levels. Each level can hold a large number of electrons, a number directly proportional to the strength of the magnetic field. His calculation of the resulting magnetic response is known as Landau diamagnetism.
Landau levels soon proved important for understanding metals. In strong magnetic fields they cause the electrical and magnetic properties of a material to oscillate as the field changes, effects named after de Haas and van Alphen and after Shubnikov and de Haas that physicists use to map the electrons inside metals.
Half a century later the idea became central to one of the great discoveries of condensed-matter physics. In 1980 Klaus von Klitzing, working at a high-magnetic-field laboratory in Grenoble, found that the electrical resistance of a thin layer of electrons in a strong magnetic field takes exactly quantised values. He received the 1985 Nobel Prize in Physics for this integer quantum Hall effect, which is explained using Landau levels.
The quantisation is astonishingly precise, matching theory to better than one part in a billion. It provided a new practical standard for electrical resistance, based on the von Klitzing constant, and an independent way to measure the fine-structure constant of quantum electrodynamics.
Why it matters
Landau's 1930 insight underpins the quantum Hall effect, which gives the world an ultra-precise standard for electrical measurement.
About Lev Landau
Baku-born prodigy who founded the great Soviet school of theoretical physics, survived Stalin’s prison, explained superfluid helium and won the 1962 Nobel Prize.
More about Lev Landau
- Lev Landau predicted a strange way plasma waves fadeIn 1946 Lev Landau predicted that waves in a plasma can lose energy without any collisions, an effect confirmed experimentally in 1964 and now called Landau damping.
- Landau co-discovered the quantum density matrixIn the late 1920s, while still a teenager, Lev Landau independently introduced the density matrix, a basic tool of quantum physics, alongside John von Neumann.
- Lev Landau explained frictionless superfluid heliumLev Landau explained why liquid helium flows without friction below 2.17 K, introducing phonons and 'rotons'; it won him the 1962 Nobel Prize in Physics.
- Landau's Fermi liquid theory explains metalsIn 1956 Lev Landau introduced Fermi liquid theory, explaining why electrons in metals and atoms in liquid helium-3 behave almost like free particles.
- The Ginzburg–Landau theory explains superconductorsLev Landau and Vitaly Ginzburg created the Ginzburg–Landau theory of superconductivity, work that helped win Ginzburg and Landau's student Abrikosov the 2003 Nobel Prize.
- Landau and Lifshitz wrote physics' great textbook seriesWith his student Evgeny Lifshitz, Lev Landau began the ten-volume Course of Theoretical Physics, still used by graduate physics students worldwide.
- Landau's 'Theoretical Minimum' trained a generationLev Landau's famous 'Theoretical Minimum' exams, passed by only 43 candidates from 1934 to 1961, created the Soviet Union's greatest school of theoretical physics.
- Landau's theory explains how matter changes stateLev Landau's theory of second-order phase transitions introduced the 'order parameter', still a broad and powerful framework for how matter changes state.
Sources
- Landau levels Wikipedia
- Lev Landau Wikipedia
- Quantum Hall effect Wikipedia
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